> I don’t code for GPUs but it seemed pretty straightforward to me:
I don't know all the words that are being used in this tweet. But the words I _DO_ understand are being used incorrectly, which is a major red-flag.
1. The temperature issues are non-sequitur, but that's where the discussion starts. There are a whole slew of power-configuration items on modern chips, none of them discussed in this set of twitter posts.
2. TLB is a CPU-issue, traditionally. I understand that Apple has an iGPU that shares the memory controller, but GPU-workloads are quite often linear and regular. It is difficult for me to imagine any step in the shader-pipeline (vertex shader, geometry shader, pixel / fragment shader) that would go through memory so randomly as to mess up the TLB. If you're saying the TLB is the problem, you need to come forth with a plausible use-case why your code is hopping around RAM so much to cause page-walks.
3. In fact, everything they say about GPUs in the thread is blatantly wrong at its face, or possibly some kind of misstatement about the peculiarity of the M1 Apple iGPU.
4. I realize that mobile GPU programmers are always talking about this "tile-based rendering" business (popular on Apple / Android phones), and I've never bothered to learn the details of it. But I can almost assure you, even in my ignorance, that this has nothing to do with TLBs at all.
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The argument simply does not track with reality, or my understanding of GPUs in general.
The vague advice I've heard for GPUs on mobile systems is to learn about the peculiarities of tile-based rendering, and to optimize for it specifically, because that's the main difference in GPU-architecture between Desktop GPUs and Phone GPUs. But nothing discussed in this set of twitter posts seems to match what I've often heard about iPhone/Android GPU programming.
I've seen the experts advice on Android/Apple phone architecture / tile-based rendering. I don't know it, but... I think I can recognize it when I see them talking. This set of twitter posts is not an expert talking.
I don't know all the words that are being used in this tweet. But the words I _DO_ understand are being used incorrectly, which is a major red-flag.
1. The temperature issues are non-sequitur, but that's where the discussion starts. There are a whole slew of power-configuration items on modern chips, none of them discussed in this set of twitter posts.
2. TLB is a CPU-issue, traditionally. I understand that Apple has an iGPU that shares the memory controller, but GPU-workloads are quite often linear and regular. It is difficult for me to imagine any step in the shader-pipeline (vertex shader, geometry shader, pixel / fragment shader) that would go through memory so randomly as to mess up the TLB. If you're saying the TLB is the problem, you need to come forth with a plausible use-case why your code is hopping around RAM so much to cause page-walks.
3. In fact, everything they say about GPUs in the thread is blatantly wrong at its face, or possibly some kind of misstatement about the peculiarity of the M1 Apple iGPU.
4. I realize that mobile GPU programmers are always talking about this "tile-based rendering" business (popular on Apple / Android phones), and I've never bothered to learn the details of it. But I can almost assure you, even in my ignorance, that this has nothing to do with TLBs at all.
-----
The argument simply does not track with reality, or my understanding of GPUs in general.
The vague advice I've heard for GPUs on mobile systems is to learn about the peculiarities of tile-based rendering, and to optimize for it specifically, because that's the main difference in GPU-architecture between Desktop GPUs and Phone GPUs. But nothing discussed in this set of twitter posts seems to match what I've often heard about iPhone/Android GPU programming.
I've seen the experts advice on Android/Apple phone architecture / tile-based rendering. I don't know it, but... I think I can recognize it when I see them talking. This set of twitter posts is not an expert talking.